Apparatus for developing latent electrostatic images

ABSTRACT

Vapor fusing apparatus comprising a substantially enclosed chamber having ingress and egress openings associated therewith. A solvent soluble powder image, formed on a support member, is delivered to the chamber through the ingress opening, the image being fused to the support member by solvent vapor generated in the chamber. The support member, after the image is fused thereto, exits from the chamber through the egress opening. The ingress and egress openings of the chamber are located above the level of maximum concentration of the solvent vapor generated in the chamber to minimize vapor loss to the atmosphere. The support member is under continuous and positive control during the fusing operation.

Schuclr.'. ..'.34/56 v D United States Patent 1151 3,704,524 Kamola et al. 1 Dec. 5, 1972 [s41 APPARATUS FOR DEVELOPING 2,726,166 12/1955 Greaves ..34/1s5 x LATENT ELECTROSTATIC 1M AGES 3,078,589 2/1963 Carlson ..34/155 X 3,149,931 9/1964 Gundlach ..34/155 [72] Inventors: Roman C. Kamola, North Rose; v

Michael Vince, Pent-161d; Robe" Primary ExaminerCarroll B. Dority, Jr. W. Gundlach, Victor; Kenneth W. Attorney-James J. Ralabate, Albert A. Mahassel, Gunther, Rochester, all of NY. 1 John E. Beck and Irving Keschner [73] Assrgnee: i220: Corporation, Stamford, [57] ABSTRACT I Vapor fusing apparatus comprising a substantially en- [22] March 1971 closed chamber having ingress and egress openings asl2l] Appl. No.: 119,775 sociated therewith. A solvent soluble powder image, formed on a support member, is delivered to the Related U.S. Application Data chamber through the ingress opening, the image being 1 fused to the support member by solvent vapor [63] fggg z g of 4 generatedin the chamber. The support member, after an one the image is fused thereto, exits from the chamber through the egress opening. The ingress and egress [52] U.S. Cl. "34/56, 34/37, 34/151, v openings of the chamber are located above the level 95/89 G 1 of maximum concentration of the solvent vapor Int. f generated in the chamber to minimize vapor loss to Field of Search the atmosphere. The support member is under con- 34/44, 56; 95/89 G I tinuous and positive control during the fusing operation. [56] References Cited 4 Claims, 5 Drawing Figures UNITED STATES PATENTS I 3,368,865 2/1968 Wu-M.NdmhmmmMy MW PATENIED DEC 5 1972 SHEEI 1 BF 3 INVENTORS ROMAN C. KAMOLA MICHAEL A. VINCE ROBERT W. GUNDLACH KENNETH W. GUNTHER iiTTOR/VEY APPARATUS FOR DEVELOPING LATENT ELECTROSTATIC IMAGES RELATED APPLICATION This is a continuation-in-part of application Ser. No. 874,423, filed Nov. 6, 1969 and now abandoned.

BACKGROUND OF THE INVENTION Xeroradiography, as disclosed in U.S. Pat. No. 2,666,144, is a process wherein an object is internally examined by subjecting the object to penetrating radiation. A uniform electrostatic charge is deposited on the surface of a xerographic plate and a latent electrostatic image is created by projecting the penetrating radiation, such as X-rays or gamma-rays, through the object and onto the plate surface. The electrostatic latent image may be made visible by contacting the latent electrostatic image on the'plate surface with fine powdered particles electrically charged opposite to the latent electrostatic imagepatte rn on theplate. The visible image may be viewed, photographed or transferred to another surface where it may be permanently affixed or otherwise utilized. The entire processing is dry and no dark room is necessary.

Xeroradiography in recent years has been utilized to detect breast cancer in women. The resolving power of the xeroradiographic plate has been found to exceed that of the conventional film utilized in roentgenography. Tests with wire mesh have shown that using standard roentgenographic film, one begins to loose detail with a mesh of 180 lines to the inch while a mesh of 1,200 lines to the inch can be recorded on a xeroradiographic plate.

In examination of breasts wherein soft tissue comprises most of the breast area, Xeroradiography, or xeromammagraphy, provides greater resolving power than the conventional roentgenographic film and greater image detail is achieved. A wide range of contrast is seen on the xeroradiographic plate as compared to the conventional roentgenographic films so that all the structures of the breast from the skin to the chest wall and ribs may be well visualized. Besides for providing better contrast, xeromammagraphy detects small structures like tumor calcification and magnifies them more than conventional film, is quicker, less expensive, gives greater detail, and requires less radiation than prior X-ray techniques.

As stated hereinabove, after the latent electrostatic image pattern on the xerographic plate is developed, the image may be transferred to another surface by techniques known to those skilled in the art. Conventionally, there are usually two methods by which the powder image is affixed to the surface of a transfer member. The first of these methods is that by application of heat in which case the powder image or its support must be formed of a thermoresponsive material, such as heat fusible resin, which flows without image distortion when heated and coalesces when cooled to ambient temperature. The second of these methods is to introduce the image-bearing member into an atmosphere of the vapor of a solvent for the developing powder as disclosed in Carlson U.S. Pat. No. 2,776,907. In the solvent vapor process, the powder image is rendered a tacky cohesive mass while in the presence of the atmosphere of the solvent vapor and usually, while still tacky, is removed to ambient air for .improvements are possible. For example, most commercially marketed machines employ a thin layer of vitreous selenium as the photoconductor. Continuous heat exposure is known to have a deleterious effect on the photoconductive properties of selenium. Dissipation or insulating of the heat, therefore, must be carefully controlled. When the image is to be fused to paper, cellulose acetate, or other base having a relatively low charring or combustion temperature, as usually is the case, the powder must be made of material which becomes adhesive at a temperature below that which will cause damage to the base. This imposes limitations on the choice of resins which make it difficult to meet other desirable characteristics in the powder composition. Furthermore, certain paper stocks, such as used in record controlled accounting cards, have controlled moisture contents which are decreased at high temperature destroying cards for their intended purpose.

Vapor fixing of powder images by means of a solvent vapor has also been put to a practical use and found to form denser images than formed by heat fusing. However, most solvents suitable for use in conjunction with these resins generally used in toners are characterized by various orders of undesirability such as obnoxious odor, toxicity, etc. For example, one such solvent found particularly suited for fusing xerographic images is trichloroethylene, which happens to be characterized by objectionable odor and a degree of toxicity which can rise to an objectionable level if allowed to escape to the room at a high rate. Other solvents which may be utilized include some of the fluorocarbon products manufactured under the name Freon, a trademark of the E. l. DuPont De Nemours Company, and dichloromethane.

Although the prior art has sought to eliminate the problem of escaping solvent vapor into the atmosphere, the problem still limits the usefulness of vapor fixing. The prior art automatic vapor fixing devices were generally concerned with continuous web surfaces having images formed thereon. The prior art fixing devices which utilize a solvent vapor chamber to fuse an image on a single cut sheet normally entailed a manual operation which substantially eliminated the loss of solvent vapor. However, the problem arises when it is desired to automatically fix powder images to single cut sheets while minimizing the loss of solvent vapor to the atmosphere and to provide apparatus which is compact, inexpensive and which provides positive control on the 7 sheets throughout he fixing operation.

SUMMARY OF THE INVENTION The present invention provides improved apparatus for fixing powder images, and, in particular, relates to apparatus for fixing powder images formed in the xeroradiographic process. The invention provides a vapor fixing chamber arranged such that the transfer member, or support surface, containing the powder image enters and exits the chamber through openings which are located above the level of maximum solvent vapor concentration thereby greatly reducing solvent vapor loss to the atmosphere. Single cut sheets having the powder image thereon are introduced into the vapor chamber through the ingress opening and automatically withdrawn through the egress opening after the image is fused to the support surface. The cut sheets are under continuous positive control during the entire operation. Closure members, such as doors, are located adjacent the openings and control means are provided to automatically control the operation of the closure members so that possible vapor loss to the atmosphere is greatly reduced.

It is, therefore, an object of the present invention to provide improved apparatus for fixing powder images.

It is a further object of the present invention to provide improved apparatus for fixing powder images to a transfer member utilizing vapor fixing.

It is still a further object of the present invention to provide novel apparatus for fixing powder images to a transfer member in a vapor fixing chamber wherein the chamber ingress and egress openings through which the transfer member passes are located above the level of maximum concentration of the solvent vapor introduced into the chamber, thereby minimizing vapor loss to the atmosphere.

It is an additional object of the present invention to provide novel vapor fixing apparatus wherein single cut sheets introduced intothe vapor chamber are maintained under continuous positive control.

It is a further object of the present invention to provide novel apparatus for vapor fixing powder images to a transfer member wherein the apparatus is compact and economical.

DESCRIPTION OF THE DRAWINGS For a better understanding of the invention as well as of objects and further features thereof, reference is made to the following description which is to beread in conjunction with the accompanying drawings wherein:

FIG. 1 is a sectional end view of the vapor fixing apparatus of the present invention;

FIG. 2 is a plan view of the vapor fixing apparatus of the present invention;

FIG. 3 is a partial sectional front view of the novel vapor fixing apparatus of the present invention;

FIG. 4 is a cross-sectional view taken on line 4-4 of FIG. I; and

FIG. 5 is a partial sectional view of the fuser illustrating solvent vapor generation.

DESCRIPTION OF THE PREFERRED EMBODIMENT Techniques for applying latent electrostatic charge patterns onto a support surface in imagewise configuration are well known in the prior art. For example, in the process of xeroradiography, as disclosed in the aforementioned U.S. Pat. No. 2,666,l44, an object is internally examined by subjecting the object to penetrating radiation. A uniform electrostatic charge is deposited on the surface of a xerographic plate and a latent electrostatic image is created by subjecting the penetrating radiation, such as X-rays or gamma-rays, through the object and onto the plate surface. The electrostatic latent image may be made visible by contacting the latent electrostatic image on the plate surface with fine Hyman:

powdered particles electrically charged opposite to the latent electrostatic image pattern on the plate. An electrostatic charge pattern may be deposited upon a substrate which has an insulating layer thereon by the electrostatic printing technique disclosed in U.S. Pat. No. 3,289,209 and subsequently developed.

The novel fusing apparatus of the present invention may be utilized for fixing any powder image applied to a support surface, such as powder images formed by the conventional xerographic process and those formed by xeroradiographic and electrostatic printing techniques mentioned hereinabove. Afterthe powder image is applied to the support surface or support material, such as single cut sheet 10 shown in FIG. 1, the sheet is conveyed to thenovel fixing apparatus of the present invention by suitable transport means, such as a vacuum transport generally indicated by reference number 12. A suitable vacuum transport for use in the present invention is disclosed in U.S. Pat. No. 3,301,126. It should be noted that the type of transport mechanism utilized to deliver the sheets is not the subject of the present invention which is directed to novel fuser apparatus.

Referring now to FIGS. 1, 2, 3, 4 and 5, the novel fuser apparatus of the present invention is comprised of a box-like structure forming a vapor chamber 20 into which the single cut sheets 10 are delivered. The chamber 20 may be made from an insulating material such as Teflon, a fluorinated ethylene-propylene resin, available from the E. I. DuPont De Nemours Company, to minimize heat loss to the atmosphere. If the chamber is to be fabricated from metal, it may be encased in the insulating material. The sheets 10, with a powder image thereon, are delivered face up to chamber 20 by vacuum transport 12 are are pulled from the chamber 20 by pinch roller 21 and drive or pick-up roller 22. As illustrated in FIG. 1, the vacuum transport 12 is preferably inclined at an angle to the horizontal. An angle of approximately 30 isillustrated in the Figure. The inclination of the vacuum transport 12 allows the sheets 10 to pass through the vapor chamber 20 without smearing the powder image. The chamber is constructed substantially vapor-tight and is formed of a front wall 24, side walls 26 and 28 and bottom, top and rear walls 30, 32, 34, respectively. Defined in the top wall 32 are entrance or ingress, and exit, or egress, openings 39 and 41, respectively. Gate or closure means 40 and 42 normally cover or close the openings 39 and 41, providing a vapor-tight chamber even if the vapor level is above the level of openings 39 and 41. The drive roller 22 is mounted on axle 44 journaled for rotation between a pair of parallel supports 45 and 47. As shown in FIG. 1, both the vacuum transport means and the drive roller 22 are driven by motor means 46. It should be noted that separate motors can be utilized to drive the transport means and the drive roller. The motor is connected to a source of electric power and is controlled by switching means (not shown). The closure means 40 and 42 are secured to top wall 32 via hinge members and 52, respectively. Mounted to the top wall 32 are solenoids 54 and 55. Wires 56 and 58 couple the output shafts of solenoids 54 and 55, respectively, around guide posts 60 and 62 to L-shaped members 64 and 66. Members 64 and 66 are mounted to hinge members 50 and 52, respectively.

A reservoir70 contains liquid solvent for the solvent soluble component of the powder image to be fused. Since a certain quantity of solvent is consumed in the process of fusing, the level of liquid solvent is maintained substantially level and constant by means of a makeup solvent 72 contained in a dispenser bottle 74 which flows solvent to the reservoir 70.

The generation of vapor within the chamber may be effected by means of a solvent wick 80 formed of felt, cloth, blotting paper or the like. The lower end of the wick is rolled into a wad at the bottom of the reservoir 70 to draw up solvent in the wick and generate a vapor atmosphere along the path of movement of the continuous sheet moving therepast. Wick 80 as shown is supported by a perforated, channel-shaped member 82 extending substantially along the length of front and rear walls 24 and 34, respectively and supported by solvent pan 84. A cone shaped upper edge sheet guide 83 is affixed at each end of the vapor chamber 20. The guides 83 prevent the powder image side of the sheet from rubbing against the bottom of solvent pan 84, thereby preventing the powder image from smearing. Guides 83 force the sheets 10 to conform fairly closely to a lower wire guide 85 as it passes through the fuser, thereby exposing the powder image to the more concentrated solvent vapors at the bottom of the chamber 20. The wire guide 85 extends the width of the chamber and is configured so that the sheet passes through the chamber below the channel 82 containing the wick 80. The cut sheet 10, when entering the chamber through the ingress opening 39, passes onto the wire guide 85 and is guided under the wick 80 through the vapor atmosphere in the chamber to the egress opening 41. It is to be noted that alternate means may be utilized to generate the solvent vapor atmosphere in chamber 20. For example, a metered nozzle arrangement may be utilized wherein a solvent aerosol is introduced into chamber 20 in short bursts on demand by means of a compressed gas source. The solvent can be pressurized in cans which would be mounted to the side wall of the chamber and activated to give a burst of solvent spray for the necessary duration when a sheet entered chamber 20. The solvents vaporize very rapidly and are introduced into the chamber in a sufficient quantity so that the reduction in viscosity of the powder image permits powder to flow into the fibers of the sheets 10. Another technique for generating the solvent vapor atmosphere is to inject a sufficient amount of liquid solvent into a conventional, heated chamber located in fuser chamber 20 whereby the solvent is vaporized into the remaining chamber area through openings in the heated chamber. A simplified apparatus for implementing this technique is shown in FIG. 5 wherein liquid solvent in container 100 is injected into heated chamber 102 via nozzle 104. The solvent is vaporized and exits through openings in the member 102 to chamber 20. The heating element for heated chamber 102 and the source for energizing the element are not shown since they are conventional.

As shown in FlGS. l and 5, a source of low heat energy may be added to vapor chamber 20 to ensure that the temperature of the vapor atmosphere is above ambient, assuming that the temperature of the surface of the incoming sheets 10 is at ambient. This enables the vapor atmosphere to condense on the cooler sheets at relatively high rates, i.e., 3 to 4 copies per minute continuously thereby fusing the powder image on the sheet surface. FIGS. 1 and 5 illustrate a thin film heater 110 operated in the range from about 20 to about 50 watts as the source of low heat energy, although other heating elements, such as a metallic strip heater, may be utilized. The electrical connections and power source for the heater (not shown) are conventional.

To prevent reaction with the solvent vapor, it is preferred that the heat energy source be insulated. For example, thin film heater 110 may be encased in Teflon film. Thin film heater 110 may be mounted to the chamber by Teflon pins 112 to minimize heat loss by conduction. If a metallic strip heater is utilized as the source, it should be mounted on insulating standoffs to also minimize heat loss.

The source of low heat energy may be mounted to the underside of the wire paper guide or above the solvent reservoir in the chamber as alternate locations to that shown in FIGS. 1 and 5. I

In operation, as the single cut sheets are conveyed by the vacuum transport 12 to the vapor fusing apparatus, the leading edge of the sheet 10 actuates a gate, or switch, means which energizes solenoid 54. The solenoid shaft is caused to move in a direction such that wire 56 pulls on member 64, thereby causing closure member 40 to rotate about hinge 50 whereby cut sheet 10 enters chamber 20 through ingress opening 39 onto paper, or sheet, guide 85. FIG. 1 shown closure member 40 in the rotated position. Stop means 92 and 94 are provided to limit the rotation of closure means 40 and 42, respectively. The solenoid 54 is continuously energized as long as the cut sheet is contacting gate 90. After the trailing edge of sheet 10 passes gate 90, the solenoid 54 is deenergized, the closure means 40 returning to its initial position to close ingress opening 39. It should be noted that preferably the dimension of the cut sheet in the direction of travel of the transport means should be at least equal to or greater than the width of the vapor fuser so that as the trailing edge of the sheet 10 is entering vapor chamber 20, the leading edge thereof is exiting through egress opening 41. This provides a continuous, positive control on the cut sheet thereby reducing the chances of sheet jam and enabling automatic operation of the fuser. When the leading edge of the cut sheet 10 reaches gate, or switch, means 95 located adjacent egress opening 41, solenoid 55 is energized and wire 58 pulls on member 66, thereby rotating closure member 42 about hinge 52. Cut sheet 10 exits from the vapor chamber through opening 41 and is picked up by rollers 21 and 22 and delivered to a utilization means (not shown). After the trailing edge of cut sheet 10 passes switch 95, solenoid 55 is deenergized and member 42 closes. It should be noted that the sequence for operation of the solenoids set forth hereinabove is merely exemplary of a type of ingress and egress opening control to minimize the loss of vapor to the atmosphere.

The control of the ingress and egress openings as described hereinabove and the delivery system wherein cut sheets are delivered to the vapor chamber at a level lower than the ingress and egress openings such that the vapor atmosphere generated by the wick does not reach the level of the openings, since the vapor is heavier than air and tends to settle towards the bottom of the chamber, provides a vapor fusing system whereby vapor loss to the atmosphere is minimized.

It should be noted that the vapor atmosphere, due to its concentration gradient, may escape through the ingress and egress openings in small concentrations. However, during the normal operation of the vapor fuser of the present invention, the maximum concentration of the vapor atmosphere within the chamber remains below the level of the ingress and egress openings.

Various flexible seal members such as polyurethane or fiber glass strips impregnated with silicone may be provided along the length of the ingress and egress openings to provide a substantially vapor tight chamber.

It should be apparent that the size of elements may be controlled by various factors including cut sheet dimensions, solvent employed, rate of cut sheet movement, developer composition, etc. in order to achieve a required vapor exposure prior to the cut sheet egressing from the vapor chamber 20. With the apparatus set forth hereinabove, powder images formed with a toner having a phenolic base with dichloromethane as solvent fuse in about 2 seconds before exiting from the vapor chamber while powder images formed with a styrene based toner fused in about 1 /4 seconds of exposure before exiting from the vapor chamber. The materials of construction for the various elements should preferably not be subjected to chemical attack for the solvent employed. For dichloromethane, various materials such as stainless steel, nylon, Teflon (in addition to its heat insulating properties as set forth hereinabove) and aluminum have been found suitable.

The invention provides high speed automatic ap paratus for vapor fusing powder images on a single cut sheet and in which the solvent vapor loss to the atmosphere is substantially reduced. The reduction in vapor loss to the atmosphere is accomplished by delivering the cut sheet to and from the vapor chamber atmosphere through openings which are located above the level of maximum concentration of the solvent vapor utilized to fix the images. In addition, the members which control the closure of the ingress and egress openings are controlled to minimize the time in which the openings are exposed to the atmosphere.

The invention provides a novel, safe and economical method of fusing images on single cut sheets containing powdered images thereon. For example, in the xeroradiography apparatus described above, the cut sheets are automatically fed to the vapor fusing apparatus of the present invention, the powder images are fused and automatically withdrawn from the fusing apparatus to be delivered to a storage area or other utilization means. As stated hereinabove, the vapor loss to the atmosphere is minimized so that objectionable odors, venilation requirements, etc. are substantially eliminated, thereby increasing the efficiency, comfort, speed and economic advantages over the prior art devices.

While the invention has been described with reference to its preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereofwithout departin from the true s irit and scope of the invention. In add: ion, many modi rcations may be made to adapt a particular situation or material to the teaching of the invention without departing from its essential teachings.

What-is claimed is: 1. Apparatus for fusing powder material having a solvent soluble component onto a support surface comprising:

means defining a substantially enclosed chamber; vapor generating means in said chamber for generating an atmosphere of solvent vapor for the solvent soluble component of the powder material in a portion of said chamber;

an ingress opening defined in said chamber and located above the level of maximum solvent vapor concentrationwithin said chamber, said support surface passing into said vapor atmosphere through said ingress opening; an egress opening defined in said chamber and located above the level of maximum solvent vapor concentration within said chamber, said support surface passing from said vapor atmosphere through said egress opening; means for transporting said support surface through said chamber portion; and

first and second closure means operably coupled to said ingress and egress openings, respectively, whereby said openings are closed by said closure means in accordance with a predetermined operating cycle.

2. The apparatus as defined in claim 1 wherein said first closure means is operative after the trailing edge of said support surface passes a first switch means, said second closure means is inoperative until the leading edge of said support surface reaches a second switch means adjacent said egress opening and said second closure means is operative after the trailing edge of said support surface exits from said egress opening.

3. The apparatus as defined in claim 2 including means to guide said support surface within said chamber portion below said vapor generating means.

4. Apparatus for fusing powder material having a solvent soluble component onto a support surface comprising:

a chamber substantially enclosed;

vapor generating means in said chamber for generating an atmosphere of solvent vapor for the solvent soluble component of the powder image in a portion of said chamber;

ingress and egress openings defined in said chamber located above said vapor generating means, said support surface passing into said vapor atmosphere through said ingress opening, and exiting from said vapor atmosphere through said egress opening, said support surfaces passing below said vapor generating means; and

closure means operable coupled to said ingress and egress openings whereby said openings are closed in accordance with a predetermined operating cycle, said closure means including solenoid means responsive to the position of said support surface.

i l k l 

1. Apparatus for fusing powder material having a solvent soluble component onto a support surface comprising: means defining a substantially enclosed chamber; vapor generating means in said chamber for generating an atmosphere of solvent vapor for the solvent soluble component of the powder material in a portion of said chamber; an ingress opening defined in said chamber and located above the level of maximum solvent vapor concentration within said chamber, said support surface passing into said vapor atmosphere through said ingress opening; an egress opening defined in said chamber and located above the level of maximum solvent vapor concentration within said chamber, said support surface passing from said vapor atmosphere through said egress opening; means for transporting said support surface through said chamber portion; and first and second closure means operably coupled to said ingress and egress openings, respectively, whereby said openings are closed by said closure means in accordance with a predetermined operating cycle.
 2. The apparatus as defined in claim 1 wherein said first closure means is operative after the trailing edge of said support surface passes a first switch means, said second closure means is inoperative until the leading edge of said support surface reaches a second switch means adjacent said egress opening and said second closure means is operative after the trailing edge of said support surface exits from said egress opening.
 3. The apparatus as defined in claim 2 including means to guide said support surface within said chamber portion below said vapor generating means.
 4. Apparatus for fusing powder material having a solvent soluble component onto a support surface comprising: a chamber substantially enclosed; vapor generating means in said chamber for generating an atmosphere of solvent vapor for the solvent soluble component of the powder image in a portion of said chamber; ingress and egress openings defined in said chamber located above said vapor generating means, said support surface passing into said vapor atmosphere through said ingress opening, and exiting from said vapor atmosphere through said egress opening, said support surfaces passing below said vapor generating means; and closure means operable coupled to said ingress and egress openings whereby said openings are closed in accordance with a predetermined operating cycle, said closure means including solenoid means responsive to the position of said support surface. 